In recent years, a vehicle air-conditioning system has been used which incorporates a cooler unit which includes an evaporator, and a heater unit, which includes a heater, as a unitary arrangement wherein the cooler and heater units are arranged serially lengthwise in the vehicle so as to provide an improved space availability in the foot area of the passenger within the vehicle, more particularly, to increase a foot-receiving space, and also to reduce the manufacturing cost. An example of such a vehicle air-conditioning system is disclosed by Japanese Laid Open Patent Application No. 250345/1998.
FIG. 3 illustrates a sectional view of the vehicle air-conditioning system as illustrated and described in the aforementioned application. The air-conditioning system 50 comprises an evaporator 52 for receiving therein an air flow that is discharged through a front portion of the vehicle into a casing of the system by a blower, and for changing the received air flow to a cooled or cold air through a heat exchanging process that can then flow rearward of the evaporator 52 and a heater 54 that is located rearward or downstream of the evaporator 52. The heater 52 receives at least a portion of the cold air flow and heats the portion of the cold air flow to a warm air that can then flow rearward from the heater 56. The air-conditioning system also comprises a partition plate 56 that is disposed rearward or downstream of the heater 54. The partition plate 56 is adapted to direct the warm air flow through the heater 54 upwardly in a manner so as to permit mixing of the warm air flow and the cold air flow being discharged from the evaporator 54 and bypassing the heater 54 thereabove. The air-conditioning system further comprises a guide wall 60 located adjacent to the partition member 56 for downwardly directing the cold air, the warm air or the mixture of cold and warm air which has passed over a top end 58 that is defined by the partition plate 56 for blowing-out such air. The top end 58 of the partition plate 56 may be in the form of a thin plate which is turned or bent forwardly. The air-conditioning system 50 also has three outlets, i.e., a defrost outlet 62, vent outlet 64 and floor outlet 66 as well as five dampers, i.e., a cold air damper 68, a warm air damper 70, a defrost damper 72, a vent damper 74 and floor damper 76.
When it is desired to operate the air-conditioning system in a so-called “bi-level” mode wherein conditioned air is discharged through the vent outlet 64 and warm air is discharged through the floor outlet 66, the defrost damper 72 is closed, the cold air, warm air and vent dampers 68, 70, 72 are half opened, and the floor damper 76 is opened. The degree to which the cold air and warm air dampers 68, 70 are opened can control a ratio of the cold and warm air to be mixed together to thereby adjust the temperature of the mixed air to be discharged. A portion of the cold air passing through the evaporator 52 can flow through the opened cold air damper 68 and then bypass the heater 54 thereabove while the remaining portion of the cold air can flow through the opened warm air damper 70 into the heater 54 where the remaining portion of the cold air is heated and becomes a warm air flow. The warm air flow being discharged rearward from the heater 54 is directed upward while impinging upon the partition plate 56 and is then redirected forwardly by the forwardly bent top end 58 of the partition plate 56. As a result, most of the forward warm air flow can meet the rearward cold air flow bypassing the heater 54 thereabove, thereby resulting in the warm air and cold air flows being mixed so as to provide a conditioned air flow which is then discharged through the vent outlet 64. On the other hand, the remaining portion of the warm air is turned through 180 degrees downwardly in the region of the top end 58 of the partition plate 56 by the vent damper 74 and the guide wall 60 and is then discharged through the floor outlet 66.
The air-conditioning system of the above-mentioned type may, however, produce considerable noise during operation of the system that can impair the operator's comfort in operating the vehicle. The inventors of the present invention have found that the warm air flow through the heater 54 may be separated from the top end portion 58 of the partition plate 56 as the warm air moves upward along the partition plate 56 and flows beyond the top end portion 58, thereby resulting in the creation of an eddy in the region of the top end portion 58 of the partition plate 56 that may lead to the considerable noise that is produced during operation of the system. Moreover, such a separation of the air flow can lead to creation of pressure loss in the air flow and a reduction in the air flow rate.
It is therefore an object of the present invention to provide a vehicle air-conditioning system which is arranged to reduce the noise that results from the separation of flow that is encountered in the conventional air-conditioning system.
Another object of the present invention to provide a vehicle air-conditioning system which is arranged so as to avoid the reduction of the air flow rate to attain a more efficient operation of the vehicle air-conditioning system.